Batch conditions

An alternative, and more expensive, technique involves the application of commercial glass inserts, which are offered by Wilmad for all commercial MAS NMR rotor types. Approximately 60 or 200 mg of catalyst powder can be filled into a 4-mm or 7-mm glass insert, respectively. After calcination of the catalyst and adsorption of reactant molecules introduced from a vacuum line, the glass insert is sealed at the waist (Fig. 7). To prevent heating of the sample, the glass ampoule is clamped in one of the chucks and cooled by liquid nitrogen. 

Another, frequently applied, approach is based on the preparation of the solid catalyst directly inside the sample volume of an MAS NMR rotor. After filling the MAS NMR rotor with the catalyst, the rotor is placed into a fitting at the bottom of a piece of specialized vacuum equipment, which is shown schematically in Fig. 8. After calcination of the catalyst under vacuum and loading with reactant molecules, the MAS NMR rotor is sealed with a gas-tight rotor cap inside the vacuum equipment. 

In more recently introduced equipment, the calcination and loading of the catalyst samples can be performed under shallow-bed conditions. For example, the equipment developed by Zhang et al. (51) (Fig. 9) allows a calcination of the powder in a horizontal tube inside a heater at temperatures of up to 1000 K. After loading of the catalyst with probe molecules or reactants, the powder is added to an MAS NMR rotor at the bottom of the equipment, sealed with a rotor cap from a plug rack, and transferred to the NMR spectrometer. As in the case of the former approaches, the samples prepared in the equipment of Zhang et al. 151) can be used for ex situ as well as in situ NMR investigations under batch reaction conditions. Furthermore, this equipment is suitable for ex situ investigations of solid-catalyzed reactions under flow conditions. In this case, the horizontal tube inside the heater is used as a fixed-bed reactor. 

Generally, several protocols are used for the characterization of sohd-catalyzed reactions under batch reaction conditions by NMR spectroscopy. In ex situ experiments, the conversion of reactants adsorbed on the catalyst is carried out in an external oven and stopped after a given reaction time by quenching, for example, in liquid nitrogen. Subsequently, the reaction products formed on the catalyst surface are investigated at room temperature by use of a standard MAS NMR probe. This protocol is repeated with a stepwise increment of the reaction time at the same temperature or with a stepwise increment of the reaction temperature for the same duration. In an in situ experiment, the catalytic conversion of the reactants is measured inside the NMR spectrometer by use of a high-temperature MAS NMR probe. 

The laser heating technique can be applied to perform temperature jumps by irradiating short laser pulses at the sample container. Ernst et al. (54) used such a temperature jump protocol to perform stop-and-go experiments. After the start of the laser pulse, the temperature inside the sample volume is raised to the reaction temperature, the conversion of the adsorbed reactants proceeds, and the H MAS NMR measurement is performed. After the laser pulse is stopped, the temperature inside the sample volume decreases to ambient temperature, and the C MAS NMR measurement is made. Subsequently, the next laser pulse is started and, in this way, the reaction is recorded as a function of the reaction time. By use of the free-induction decay and the reaction time as time domains and respectively, a two-dimensional Fourier transformation leads to a two-dimensional spectrum, which contains the NMR spectrum in the Ej-dimension and the reaction rate information in the Ts-dimension (54,55). 

An alternative, and more expensive, technique involves the application of commercial glass inserts, which are offered by Wilmad for all commercial MAS NMR rotor types. Approximately 60 or 200 mg of catalyst powder can be filled into a 

---

Considering the formation of saturated five-membered heterocycles with two heteroatoms, it is worth to note the possibility to prepare 1,3-dioxolanes, dithiane, oxathianes 148 [93] and dioxolanones 149 [94] by condensation of the corresponding carbonyl compounds under microwave irradiation in acid medium (Scheme 52). The reaction, which is very useful for the protection of carbonyl compounds or for the preparation of useful synthetic intermediates, has also been carried out under batch conditions over Montmorillonite KIO clay in more than 150 g scale, using a 1 L quartz reactor [95]. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

Regarding submerged plants, sorption of Cu(II) by Myriophyllum spicatum L. (Eurasian water milfoil) has been shown to be fast and fits isotherm models such as Langmuir, Temkin, and Redlich-Peterson. The maximum sorption capacity (c/lll l j ) of copper onto M. spicatum L. was 10.80 mg/g, while the overall sorption process was best described by the pseudo-second-order equation.115 Likewise, Hydrilla verticillata has been described as an excellent biosorbent for Cd(II). In batch conditions, the qmsx calculated was 15.0 mg/g. Additionally, II. verticillata biomass was capable of decreasing Cd(II) concentration from 10 to a value below the detection limit of 0.02 mg/L in continuous flow studies (fixed-bed column). It was also found that the Zn ions affected Cd(II) biosorption.116... 

It is believed that SCR by hydrocarbons is an important way for elimination of nitrogen oxide emissions from diesel and lean-burn engines. Gerlach etal. [115] studied by infrared in batch condition the mechanism of the reaction between nitrogen dioxide and propene over acidic mordenites. The aim of their work was to elucidate the relevance of adsorbed N-containing species for the F>cNOx reaction to propose a mechanism. Infrared experiments showed that nitrosonium ions (NO+) are formed upon reaction between NO, NOz and the Brpnsted acid sites of H—MOR and that this species is highly reactive towards propene, forming propenal oxime at 120°C. At temperatures above 170°C, the propenal oxime is dehydrated to acrylonitrile. A mechanism is proposed to explain the acrylonitrile formation. The nitrile can further be hydrolysed to yield... 

Franco DV, Da Silva LM, Jardim WF (2009) Reduction of hexavalent chromium in soil and ground water using zero-valent iron under batch and semi-batch conditions. Water Air Soil Poll 197(4) 49-60... 

Na+ and K+ with a detection limit of 10 9 M. The sensor compositions exhibited wide response ranges between 10 9 and 10 5 M Na+ or K+, and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2-7.3. 

In addition to the enzyme s amino acid sequence, other parameters can affect the outcome of a biocatalytic process. For instance, a similar outcome in the aforementioned DERA-catalyzed statin synthesis was achieved by process improvements [21]. Using a thermostable variant of DERA (thermostability generally correlates well with tolerance to high concentrations of organic reagents or cosolvents), and fed-batch conditions, an efficient process that overcame sensitivity to high concentrations of chloroacetaldehyde was developed. 

Recently published examples of continuous-flow organic microwave synthesis include, for example, 1,3-dipolar cydoaddition chemistry in the CEM CF Voyager system (see Figs. 3.23 and 3.24). The cycloaddition of dimethyl acetylenedicarboxy-late with benzyl azide in toluene was first carefully optimized with respect to solvent, temperature, and time under batch conditions. The best protocol was then translated to a continuous-flow procedure in which a solution 0.33 m in both build-... 

The sequential batch reactor (SBR) consists of a vessel operated under batch conditions according to the time schedule reported in Fig. 3. The symbols Fill, React, Settle, Draw and Idle refer to the typical sequential phases of operation loading, reaction, biophase settling, discharging and the idle time. The reaction period may be split into two sub-phases an anaerobic phase and an aerobic phase. The aerobic sub-phase is devoted to convert products of the azo-dye anaerobic... 

The assessment of reaction kinetics by means of batch tests may be strongly affected by dye adsorption on the biophase and supports. The relevance of the adsorption phenomena of dyes on biophase has been addressed in studies regarding free cells [41], granular support biofilm [24], entrapped cells [11, 18], anaerobic sludge [10,24,31,34] and biological activated carbon (BAC) [42,45,47,48]. They have pointed out that the kinetics may be overestimated if the assessment of the adsorption contribution to the dye removal is not taken into account. Under batch conditions, the dye is fastly split between the liquid phase and the biophase, resulting in a sharp reduction of the dye concentration in the liquid phase until adsorption equilibrium is approached. The rate of dye adsorption must be estimated and ruled out in the kinetic assessment. 

Anaerobic phase. Nitrogen was sparged at 5 nL/h and the liquid feeding was stopped. The concentration of acid orange 7 at the beginning of the anaerobic phase was set at the pre-fixed value by injecting concentrated dye solution into the reactor. The reactor was operated under batch conditions with respect to the liquid phase. 

Fig. 6 Acid orange 7 and phenol concentration in the internal loop airlift reactor operated with Pseudomonas sp. 0X1 biofilm on natural pumice. (A) Aerobic phase. Gas air. Liquid continuous feeding of phenol supplemented synthetic medium. (AN) Anaerobic phase. Gas nitrogen. Liquid batch conditions, dye supplemented medium...

Experiments were conducted at a pressure of 40-70 bar, a temperature of 100-220°C, and reaction times of 4-390 s. It was cross-checked and confirmed that the textbook recommended reaction time of 2 h at least roughly constitutes the actual kinetically needed reaction time at the standard batch conditions of 100°C and 1 bar (which is usually not the case over-reaction is common in organic synthesis). 

A simple model of the batch process was compiled using a commercial spreadsheet program, using finite time elements. A macro was written to obtain convergence of start and end of batch conditions. This model was simple to construct and proved satisfactory in calculating the batch profiles for operation without, and subsequently with, the catalytic reactor on-line. The values obtained for operation without the inloop catalyst compared well with plant values. 

This chapter reports on the reactivity of organic carbonates as alkylating agents, with emphasis on the lightest term of the series, DMC. Under both CF and batch conditions, DMC can react with a number of nucleophilic substrates such as phenols, primary amines, sulfones, thiols, and methylene-active derivatives of aryl and aroxy-acetic acids. The mechanistic and synthetic aspects of these processes will be elucidated. 

Accordingly, under different conditions, DMC is used as a methylating reagent for a variety of substrates phenols, thiols, thiophenols, aromatic amines, arylace-tonitriles, arylacetoesters, aroxyacetonitriles, aroxyacetoesters, alkylarylsulfones, benzylarylsulfones, and lactones, either under CF or in batch conditions. 

Under batch conditions, methylations with DMC must necessarily be run in sealed autoclaves, given its boiling point (90°C) and the reaction temperature (>160°C). Batch methylations with DMC can be performed on a number of different substrates and, under such conditions, the reaction mechanism can be conveniently investigated in fact, the sampling of the reaction mixture at different conversions, and the identihcation of possible intermediates (see later) is easier with respect to CF-processes. For compounds that are susceptible to multiple methylation, the results are of special interest, since methylation with DMC totally inhibits multiple substimtion in both N- and C-alkylation, for primary aromatic amines and for CH2-active compounds, respectively. 

In summary, all the nucleophiles indicated up to now are efficiently methylated (and monomethylated, where applicable) with DMC, both under CF and batch conditions. 

The pot furnace was constructed so that the radiant heat flux, which would prevail at the top of the fuel bed in a traveling grate stoker or incinerator, could be simulated under batch conditions. The burning rates could be determined by measuring the weight loss of the fuel bed as a function of time. The pot was constructed in two sections (Figure 1)- the overbed section (combustion system) and the fuel bed section (conversion system). Secondary air (overfire air) was supplied at a number of... 

Fig. 8.44 Adsorption and desorption of Cr(VI) by a telluride alluvium in (a) a flow-through column experiment and (b) on alluvium under batch conditions (Stollenwerk and Grove 1985)...

Various tungsten-hydrido compounds prepared on silica [38], silica-alumina [39] or alumina [40] supports have been tested in propane metathesis under batch conditions to compare their properties with those of the silica or alumina-supported tantalum hydride(s) 3 [41]. 

We are starting with the case where we have a control sample that covers the whole analytical process inclnding all sample preparation steps. The matrix of the control sample is similar to that of the routine samples. Then the standard deviation of the analysis of this sample (under between-batch conditions) can be used directly as an estimate for the reproducibility within the laboratory. The standard deviation can be taken directly from a control chart for this control sample (see chapterl3). In the table two examples are shown for different concentration levels. 

The measurements on the control sample usually are made with each batch and finally marked on the control chart are done under between-batch conditions. Therefore the standard deviation for the calculation of the limits should also be determined under the same between-batch conditions. The most common way to estimate this standard deviation is to use the results from a pre-period of about 20 working days. The use of the repeatabihty standard deviation would result in too narrow limits whilst interlaboratory conditions would lead to limits that are too wide. 

Linear regression results show that b is approximately 0.5 for each experimental condition and that a increases with the rate of crystal growth due to environmental conditions. The refrigerant subcooling, aT, was seen to directly effect the value of a, whereas, since the bulk subcooling changed with time, there was no clear correlation between a and aT),. Further work will be necessary to delineate these relationships for both batch and semi-batch conditions. 

Figure 2. Change in average crystal size with time for ice ciystal seeds grown in 6% lactose under semi-batch conditions with removal of crystal slurry.

A significant improvement in the conduction of this reaction was reported under microflow conditions in comparison with batch mode. Batch conditions involved a reaction time of 60 h at room temperature to afford the final product in a 62% yield. Under optimized microreactor conditions, the online HPLC-determined yield was 91 % in a 60 min reaction time (Scheme 2). Note that the microreactor setup allowed the reaction temperature to be higher than the atmospheric boiling point of the solvent. 

Reactions were conducted at room temperature. The monolithic design of the device led to the increased safety of the process. The authors assigned the variable yield of the reaction to the non-optimized conditions. However, they have proved the principle of conducting the reactions containing diazonium salts in a safe way at room temperature, which is not possible on macroscale and batch conditions. 

Initial experiments were performed with a Baylis-Hillman setup, with p-nitrobenzaldehyde and methyl acrylate, in the presence of DABCO as catalyst (Scheme 39). Optimized conditions with a 118 min residence time (30% faster than the required time under batch conditions) at room temperature and 0.4 ml/ min flow resulted in encouraging conversions and yields (up to 93 and 82%, respectively). 

The commercial CYTOS College System [18] was used in this work. The imine was preformed in batch. After the optimisation, similar yields in comparison to the batch conditions were obtained with productivities of 8.2-10.7 g/h (Scheme 41). 

---